Analysis & Opinion

Oct 9 (Reuters) - Children's risk of developing
attention-deficit/hyperactivity disorder (ADHD) later in life
may be tied to how much fish their mothers ate while pregnant,
according to a U.S. study.

Researchers writing in the Archives of Pediatrics &
Adolescent Medicine found that eating at least two servings of
fish per week was linked to about a 60 percent lower risk of
kids developing certain ADHD-like symptoms.

But elevated mercury levels, which can also come from eating
more fish - depending on the fish - were tied to a higher risk
of developing the symptoms, such as hyperactivity, impulsiveness
and inattentiveness.

Though the study did not prove cause and effect, and did not
use a formal diagnosis of ADHD, it may offer insights into a
condition that's estimated to have an impact on one in 10
children in the United States, researchers say.

"The really important message is to eat fish," said Sharon
Sagiv, the study's lead author from the Boston University School
of Public Health.

"Just stay away from mercury-containing fish, because these
protective effects are pretty important."

Sagiv said it's best to stay away from "big fishes," such as
tuna and swordfish, which typically contain the most mercury.
Instead, stick to fishes such as haddock and salmon.

Past studies looking at the link between mercury and ADHD
have produced conflicting results.

For the new study, the researchers followed 788 children who
were born near New Bedford, Massachusetts, between 1993 and
1998. They used hair samples taken from the mothers right after
delivery to test their mercury levels, and food diaries to see
how much fish they ate.

Then, once the children were about 8 years old, the
researchers asked their teachers to evaluate the kids' behaviors
to see how many exhibited ADHD-like symptoms.

After taking all of the information into account, the
researchers found 1 microgram of mercury per gram of a mother's
hair - about eight times the average levels found in similar
women's hair in another analysis - was tied to about a 60
percent increase in the risk of their child exhibiting ADHD-like
behaviors.

But there was no link below 1 microgram of mercury per gram
of a mother's hair.

Sagiv added that the negative effects from lower levels of
mercury may be canceled out by the benefits from eating fish.
The children appeared to be 60 percent less likely to exhibit
impulsive or hyperactive behaviors if their mothers ate two or
more servings of fish per week.

That finding conflicts with the U.S. government's
recommendation that says pregnant women should eat no more than
two six-ounce servings of fish per week to limit their exposure
to mercury.

"I think it does call into question those guidelines, but
this is only one study and the results should be confirmed,"
Sagiv told Reuters health.

In an editorial that appeared with the study, Bruce Lanphear
at Simon Fraser University in Vancouver, echoed Sagiv's advice
on avoiding "big fishes."

In the long term, we have to really find ways to fight
contamination levels in fish so years from now we don't have to
give this advice," he added.
SOURCE: bit.ly/Ms92Cy
(Reporting from New York by Andrew Seaman at Reuters Health;
editing by Elaine Lies)